TOWARDS INTERBREED IBD FINE MAPPING OF THE MH-LOCUS - DOUBLE-MUSCLINGIN THE ASTURIANA-DE-LOS-VALLES BREED INVOLVES THE SAME LOCUS AS IN THE BELGIAN-BLUE-CATTLE BREED

The Spanish ''Asturiana'' cattle breed is characterized by the segrega tion of a genetically determined muscular hypertrophy referred to as d ouble-muscling or ''culones''. We demonstrate by linkage analysis that this muscular hypertrophy involves the mh locus previously shown to c ause double-muscling in the Belgian Blue cattle breed, pointing toward s locus homogeneity of this trait across both breeds. Moreover, using a twopoint and multipoint maximum likelihood approach, we show that fl anking microsatellite markers are in linkage disequilibrium with the m h locus in both breeds albeit with different alleles. Finally, we disc uss how allelic homogeneity across breeds might be exploited to achiev e efficient genetic fine-mapping of the mh locus.